Hangover symptoms and other residual effects of intoxication (hence-forth called residual effects) may be an important but poorly recognized risk factor in many injuries. The long term goal of this study is to reduce alcohol-related injuries through expanding the understanding of alcohol's role in injury risk to also include residual effects of intoxication. We intend to use this information for preventing further injuries and/or hazardous drinking by including recent intoxication assessments as part of routine screening programs for alcohol problems in critical care. We will identify and quantify the role of residual effects in traffic injuries by assessing biomarkers of recent alcohol consumption in urine among Motor Vehicle Crash (MVC) drivers admitted to the University of Maryland R. Adams Cowley Shock Trauma Center (STC) as well as all driver deaths from the medical examiner for the entire state of Maryland for 4 years. This study is an innovative use of two alcohol consumption biomarkers, ethyl glucuronide (EtG) and ethyl sulfate (EtS) in urine as indicators of residual effects even when blood alcohol is zero. The specific hypotheses behind the proposed research are: 1) impairment from residual effects of intoxication increases the risk of traffic injuries; and 2) the prevalence of residual effects of intoxication is elevated among those injured drivers with a zero BAC who were responsible for causing their crash compared to those determined not responsible. Aim 1 defines the quantitative relationship between biomarkers for residual effects, self-reported recent drinking behavior and alcohol problems, time of last drink, and symptom scores from the validated Hangover Scale among drivers able to be interviewed in hospital. Interviews will include information on current drinking patterns, CAGE, and hangover symptoms and linked to biomarker results to cross-validate the EtG/EtS estimates of residual effects. Drinking patterns including the place of last drink will also be conducted. Aim 2 quantifies risk factors for injury associated with residual effects using a case-crossover study among interviewed patients. This case-control variant compares drinking during the day immediately prior to the injury (case period) with drinking on the same day the preceding week (control) and can estimate injury risks associated with residual effects. Testing for other drugs allows stratification of results by presence or absence of drugs causing impairment. Aim 3 identifies the extent to which injured zero BAC drivers with biomarker evidence of residual effects are likely to be responsible for causing their crash, compared with zero-BAC drivers without biomarker evidence. This risk factor study involves linkage with police crash reports. Aim 4 determines the prevalence of elevated biomarkers for recent alcohol consumption among BAC zero MVC admissions and deaths. Aim 5 establishes the contribution of residual effects to all alcohol-involved serious MVC injuries and deaths and seeks to improve estimates of the alcohol-attributable fraction for traffic injuries. This novel use of biomarkers provides an unparalleled opportunity to advance understanding of the expanded role of alcohol in traffic injuries. PUBLIC HEALTH RELEVANCE: Accomplishing the study aims will increase our understanding of the full extent of alcohol's role in traffic injuries and expand the spectrum of alcohol-related problems to include the period of time after BAC is no longer elevated. Transportation and workplace regulations regarding alcohol use have largely ignored risks associated with residual effects of intoxication, and documentation of these risks could lead to improved regulations to protect public safety. The ability to objectively identify patients with evidence of residual effects post-intoxication will also enhance current clinical practice as they can be targeted for prevention efforts to either reduce or eliminate hazardous drinking, and reduce the risk of serious injury or death to both the driver impaired from residual effects and the general public.